Do Light Roasts or Dark Roasts Have More Caffeine?

If you’re looking for maximum pick-me-up, you might want to reach for a medium roast coffee.

Berry College Assistant Professor of Physics Zachary Lindsey, his students, along with analytical chemist Joshua Williams from Drexel University, conducted research that found roast degree affects caffeine concentration in light, dark or medium coffee roasts.

Lindsey decided to conduct this study after he noticed a lack of definitive scientific research to confirm if dark or light roast coffee contained more caffeine. His research team included senior physics majors, Pierce Splichal from Bishop, Ga. and Nathan Moore from Sharpsburg, Ga.

The team found two competing factors affect caffeine content: the roasting process and the extraction yield of the brew. Under identical brewing conditions, light and medium roasts typically result in higher levels of caffeine.

“Our results show that coffee loses caffeine during the later stages of roasting,” Lindsey said. “While an ultra-light roast may have the most caffeine packed into the roasted coffee seeds, the low porosity makes it much more difficult to extract that caffeine into your cup. If it’s caffeine that you want, our data suggest that a medium roast is generally a solid choice.”

Lindsey says he’s been a coffee nerd for a long time.

“Back when I was an undergraduate, my buddies and I preferred coffee shop hangs over keg parties. As a physicist, countless questions constantly nip at my heels while roasting, grinding, brewing, or consuming this mysterious aqua vitae,” he said.

Optimal caffeine extraction occurs for coffees roasted to a level that achieves sufficient porosity (to drive efficient extraction) while minimizing caffeine losses due to sublimation (occurring in later roasting stages).

Due to the numerous variations in green coffee, roast profiles, and brew methods out there, it’s difficult to establish a universal law relating roast degree and caffeine content. However, results from this study showed that caffeine extraction tended to peak in medium-roasted coffees due to the combination of higher porosities than lighter roasts and more remaining caffeine than darker roasts, according to the study.

While light-roasted coffees contain the most caffeine, the increased porosity in medium roasts makes it a little easier to get that caffeine into your cup.